I just used Royal Purple. No need to add any additive or anything like that.

 

interesting I thought Amsoil recommended it's own friction modifier if you needed to add more than is already in their oil

I prefer to use a gearoil with no friction modifier already in them these clutches are already weak IMO

if you do buy the Ford modifier don't open it until you need it and if you don't use it all triple baggie it the stuff smells horrific

'

 

Agreed^^^^

No need to use any friction modifier with Amsoil.

 

Just did mine, with same product the 75/140.. No need for diff additive with amsoil.. it is already incorporated in it. the diff additive is some differentials no matter how great the lube is can chatter, based on what type of limited slip it is. But on the 10.5 sterling in the 6.4.. No need. I dealt amsoil for a while, and spoke to technician at amsoil about this same question. My only suggestion is do it sooner than later also advanced sells a gasket to use so you don't have to solely rely on the silicone for sealant. I used permatex black, very small bead on the cover in the groove, and then a small bead on the gasket that touches the housing, and when I say small like 1/4" bead. I followed the recs snug it up, wait an hour then torque, then wait 24hrs before refilling. and worked awesome. Make sure you really clean the gears, and the housing, and the cover and the mating surface. Brake Kleen will be your friend. PS the gear oil stinks

 

I plan on adding a HYTEC, would you use the RTV as well since they have a gasket on the cover?

 

how many shops wait 24 hours or 24 minutes

0 many

rtv only bolt it on fill er up drive it

i think the Hytec has an oring and needs no sealant

 

Correct, the Mag HyTech cover does have an oring. No sealant needed. I do carry these. Don't mind that it's linked to the 99-03. It's the same cover for all sterling 10.25 and 10.5 trucks to current year.

http://cncfabricationllc.com/index....in/99-03-axle-components/mag-hytec-12-10-25-5-differential-cover-f12-10-25.html

 

Its actually amazing how many shops will drive it out 30 sec after bolting the cover back on and filling, hand you the keys, and off you go with the rtv minutes old lol. Whenever I have done it, I always do the diffs first then move on to an oil change, brakes, tire rotation, or some other maintenance to give the stuff a chance to set. Its rare for someone to come in just for the diff fluid... There is always trans, transfer case, oil change, fuel filters, and or some other repair being done.

 

Not a bad idea, but if I did that, I think I'd leave my gear lube/fill plug someplace that can't be missed before moving the truck. You go off to another job like brakes, tire rotation, fuel filters, etc. You wouldn't want to get sidetracked and forget your diffs are still empty.
The older you get, the easier it is to forget something. :senile:

 

Agreed even some/all permatex RTV's suggest the waiting ( 1 hour IIRC ) and final tighten sequence


with the AL covers i don't wait and i use the permatex copper (no waiting) https://www.permatex.com/products/g.../gasketing/permatex-ultra-copper-maximum-temperature-rtv-silicone-gasket-maker/
steel covers I prefer a gasket and rtv now if i had leaks ever i may re evaluate the waiting period

 

hey I was just taking no chances so many leaking diffs I see going down the road.

 

I read people blasting the gears with brakleen...is this standard? I was going to drain and wipe clean. The idea of that solvent in my diff gives me the heebie jeebies.

 

^^^ IMO that's a terrible idea. Drain and wipe clean :thumb:

I just apply a healthy bead of RTV to the cover, smear it flat-ish with my silicone applicator tool (finger), let it sit maybe 30 min then stick it on. Haven't had one leak yet.

 

Agreed
while it's probably fine
if i was going to clean them off i would rather use wd 40 than a caustic cleaner

but i don't see it as necessary the real key is cleaning the ring gear pocket out at the bottom of the housing thats where all the heavy debris settles

 

hammered mine with brake clean, got every particle of crap off, also a pain to clean bottom of housing because of the little pockets but took time and cleaned it all out... then filled diff, rolled very slow up the street to coat entire gear then off I went no issues.

 

Used royal purple and installed one of those $58 factory diff covers. Used grey adhesive silicone and put on with bolts slightly loose then tigntened them the next morning to provide some compression on the surface. Fill with the lube (did not add any addl friction modifier other than what is formulated into the oil) and works fine!

 

Got around to the swap today. I def recommend the maintenance if you do any hard pulling. Here is my old cover. The lower has cooked oil, similar to what you find in an oven drip pan...

Ended up going with the RP Max Gear. I can't help but think those gears are happier now...purdy too.